The present invention relates to an underride protection bumper for a truck. That is, the present invention is a bumper for a truck which prevents or minimizes the possibility of another vehicle underriding the truck or similar vehicle. The present invention further relates to a truck or similar vehicle having such an underride protection bumper.
Truck semitrailers typically have an elevated floor. That is, the floor of such semitrailers is relatively high compared to the front end of cars and pickup trucks. Therefore, if a car or pickup truck hits the rear of a semitrailer or similar vehicle with an elevated floor, the front end of the car or pickup truck may travel under the floor of the semitrailer and the passenger compartment of the car or pickup truck may slam into the rear of the semitrailer body in such a way as to completely smash the upper half of the passenger compartment, often severely or fatally injuring those in the passenger compartment of the vehicle which is said to be underriding the truck semitrailer.
In order to minimize such underride collisions, trucks have used various bumpers. Although such bumpers have been useful, they generally collapse if the impinging vehicle is going at a sufficiently high speed, leading to an underride collision. A dilemma in the design of such bumpers is that making the bumper so strong as to not collapse also leads to severe injuries or fatalities to the passengers in the underriding or impinging vehicle. That is, if the bumper of the truck is so strong as to completely avoid underriding, the kinetic energy of the collision is generally forced back into the impinging vehicle. If the impinging vehicle is going at a sufficiently high rate of speed, this kinetic energy will cause severe, often fatal, injuries to the passengers. Thus, designing the bumper of a truck to have great strength will cause severe injuries from the kinetic energy being applied to the impinging vehicle, whereas designing the bumper to collapse at a sufficiently high rate of speed will cause the severe injuries and fatalities associated with an underride collision. In general, such bumpers are helpful if the differential speed between the impinging vehicle (the vehicle which may underride) and the truck semitrailer is below a particular value.
One kind of step bumper which has been used to try to minimize underride has the step bumper itself extending between two vertical posts, one mounted on each side of the rear of the semitrailer. The step bumper extends from side to side at the lower end of the vertical posts. A brace on each side extends up from the bottom of the vertical post forward and inclined at an angle towards the trailer. These inclined braces or side members on each side collapse if the impinging vehicle hits the bumper with too much speed.
Another design uses vertical posts mounted at each side of the rear of the vehicle, which vertical posts are hinged at the upper end to the top of the semitrailer. The bumper extends between the two vertical posts at the bottom of the vertical post. A crash shock absorber is mounted at each side of the bumper to absorb shock as the bumper is pushed towards the front of the semitrailer by an impinging vehicle. The impinging vehicle collapses the shock absorbers as the vertical posts pivot about their upper hinges or pivot points. Again, this may prevent underride if the impinging vehicle is going sufficiently slowly, but the shock absorbers will be overwhelmed if the differential speed between the impinging vehicle and the semitrailer is sufficiently high. The dilemma mentioned above would again be present in this design. If the crash shock absorbers were made sufficiently strong, underride collisions could be prevented even if the impinging vehicle is going relatively fast. However, in that case, the impinging vehicle would be absorbing huge amounts of kinetic energy as though the impinging vehicle had crashed into a brick wall. The passengers might be in no better condition than they would be if an underride collision had occurred.
Generally, such step bumpers of prior designs are made to withstand about 40,000 lbs. in force before collapsing. This might be equivalent to about 15 to 20 miles per hour differential speed between the impinging vehicle and the semitrailer for a typical car or pickup truck.